The goal of this study is to measure the sampling range and effective sampling area of a semiochemical attractant-baited trap system used for western pine beetle (WPB, Dendroctonus brevicomis) at 4 locations in the western United States. To determine the probability of long-range beetle recapture, we used beetles labeled with fluorescent powder released at a central point within an array of pheromone-baited traps (16-funnel Lindgren funnel traps with attractant lures of frontalin, exo-brevicomis, and myrcene or alpha-pinene) distributed in cardinal directions at intervals from 50 to 1500 m. Weather data were recorded for each release-recapture period. Trap contents were collected from 1-3 days following each release and examined under fluorescent light to determine recapture of marked beetles. In 2006, we conducted 4 releases each in June and August that corresponded to the first and second generations of WPB in the Blue Mountains of northeastern Oregon. In 2007, we again conducted trials in northeastern Oregon (9 releases), and also in central Oregon (7 releases), western Idaho (7 releases), and northern Arizona (7 releases). Trials were conducted early and late in the flight season in each location corresponding to different WPB generations.

Results/Conclusions

Over all releases in 2006, we found >80% of all WPB recaptured in northeastern Oregon occurred within 100 m of the release point and recapture rate over all distances averaged 33%. In 2007, we observed mean recapture of 22% in northeastern Oregon and 80% of all recapture occurred within 186 m. Eighty percent of recapture occurred within 174 m in central Oregon, 143 m in Idaho and 75 m in Arizona. Recaptures rates over all dates at these locations varied from 12 to 17%. In northeast Oregon in 2006, recapture rate among traps in the four cardinal directions were unaffected by the prevailing NNW winds. In 2007, recapture at this site appeared to be somewhat elevated at traps upwind of the release point, especially within 175 m of this point. Knowledge of sampling range and effective sampling area of this trap systems could greatly enhance the value of this tool providing information about effective placement of traps for monitoring or use in suppression, and potentially in inference of beetle densities within a particular area.